Which of the following is called the Prime Meridian?

Question

Accepted Answer

The correct option is 4:
The Prime Meridian is defined as the zero-degree (0°) longitude line on the globe. This imaginary line runs from the North Pole to the South Pole, passing through the Royal Observatory in Greenwich, London, which is why it is often referred to as the Greenwich Meridian. The Prime Meridian is crucial because it serves as the reference point for measuring longitude, dividing the Earth into the Eastern Hemisphere and the Western Hemisphere. It is also the basis for calculating time zones around the world, as Coordinated Universal Time (UTC) is based on the solar time at the Prime Meridian. Every location on Earth is measured east or west of this fundamental 0° line.

The incorrect option is 1:
23°30' North is not the Prime Meridian; it is the latitude known as the Tropic of Cancer. Latitude lines run horizontally around the globe and measure distance north or south of the Equator, not east or west. The Tropic of Cancer marks the most northerly circle of latitude at which the sun can be directly overhead. This line is significant for defining Earth's climate zones, specifically the boundary of the Northern Hemisphere's tropics, and has nothing to do with defining the zero line of longitude.

The incorrect option is 2:
23°30' South is also a line of latitude, specifically the Tropic of Capricorn. Just like the Tropic of Cancer, it measures distance south of the Equator and does not serve as a longitudinal reference point. The Tropic of Capricorn is the most southerly latitude where the sun can be directly overhead at noon. It plays a role in defining the boundary of the Southern Hemisphere's tropical zone and is fundamentally different from a meridian, which measures east-west location.

The incorrect option is 3:
82°30' East is a specific line of longitude, but it is not the Prime Meridian. This particular longitude is extremely important to India because it is designated as the Indian Standard Time (IST) meridian. While all meridians are crucial for geographical referencing, only the 0° line is internationally accepted as the starting point for all longitude measurements and is uniquely named the Prime Meridian. All other longitude lines are measured in degrees east or west of this 0° reference line.